Hydraulic pumps presently exist in the prior art. These pumps include a diaphragm, an inlet passage, a discharge passage, a transfer chamber filled with a hydraulic fluid that is separated from a pumping chamber by a diaphragm, and a piston assembly defining one end of the transfer chamber and adapted for reciprocating movement between a compression stroke and a return stroke. During operation, the piston moves toward (compression stroke) and away from (return stroke) the diaphragm or into and out of the transfer chamber thereby causing such reciprocating movement to be transferred, via the hydraulic fluid in the transfer chamber, to the diaphragm. As the piston moves away from the diaphragm, the diaphragm flexes away from the transfer chamber, allowing the system fluid, such as ammonia, to be drawn into the pumping chamber through the inlet passage. As the piston moves toward the diaphragm, the diaphragm moves accordingly, flexing away from the pumping chamber and causing the fluid in the transfer chamber to be discharged through the discharge passage.
Although most of the prior diaphragm pumps discussed above functioned sufficiently well when there was a ready supply of hydraulic fluid at the inlet to the pumping chamber, such pumps had a tendency to cavitate in the pumping chamber as there was not always a ready supply of hydraulic fluid available. Attempts to solve this problem have provided a ready supply of hydraulic fluid and thus decreased the rates of cavitation. However, these attempts have invariably provided an excess of hydraulic fluid to the pumping chamber and thus decreased the effective area of the pumping chamber and thus decreased the stroke length of the piston and increased the pressure in pumping chamber. Accordingly, the efficiency of these pumps has suffered as they have not been able to operate at optimum pressures.
Additionally, these prior pumps could not discharge the pumping fluid through the discharge passage into the system below atmospheric pressure. Absorption heating and cooling systems operate more efficiently at pressures below atmospheric. In order to operate more efficiently, these systems typically include a compressor to pressurize the pumping fluid (system solution) to pressures below atmospheric. Applicant has recognized that it would be advantageous to obviate the need for a compressor in the system by providing the solution to the system under atmospheric pressure and still prevent cavitation of the pump.